1. Field of the Invention
The invention relates to medical appliances and somewhat more specifically to endocardial electrodes for intracardial stimulation of a heart.
2. Prior Art.
The art is aware of endocardial electrodes comprised of an elongated electrical conductor encased or enveloped within an electrical insulator and having an electrode head or tip on the distal end of such conductor for transmitting stimulating impulses to the heart pursuant to the controlled application of an electrical current to the conductor. In endocardial electrodes of this type, the electrode head or tip is composed of a heart compatible material which is not receptive to heart tissue growth thereabout so that such electrode tip merely loosely rests on the stimulable heart muscle. Such an endocardial electrode is rather easily removed or accidentally displaced from the stimulable muscle so that the current density on such muscle is reduced and presents a danger to the heart patient.
U.S. Pat. No. 3,953,864 suggests an endocardial electrode having a somewhat cage-shaped electrode head with spaces between the external periphery-defining edges thereof for tissue growth after positioning of such electrode in the heart. After tissue growth, this type of electrode cannot be removed or accidentally dislodged from the stimulable heart muscle. However, this electrode is disadvantageous in that a comparatively high stimulation threshold is present because of the non-stimulable cellular and/or connective tissue growths forming about the electrode head. A further disadvantage of this electrode is the relatively complicated construction thereof.